Picture of the Day: The Cave of Crystal Giants

980 ft (300 m) beneath the surface of Naica, Chihuahua, Mexico is a mine filled with giant gypsum crystals. Known locally as Cueva de los Cristales (Cave of the Crystals), the gypsum crystal cave is 98 ft (27 m in length) and connected to a larger, working mine best known for its selenite crystals.

The cave’s largest crystal found to date is 12 m (39 ft) in length, 4 m (13 ft) in diameter and 55 tons in weight. The cave is extremely hot, with air temperatures reaching up to 58 °C (136 °F) with 90 to 99 percent humidity. The cave is relatively unexplored due to these factors. Without proper protection, people can only endure approximately ten minutes of exposure at a time.